Heretofore, in sorting bearings such as needle bearings, they were allowed to slide down between rotating cylinders whose axes were mounted in a diverging manner so as to provide a gradually enlarging gap therebetween. As the bearings slide down the cylinders, they would drop through the cylinders at the point where the width of the gap was slightly greater than the diameter of the bearing. There would be no problem in sorting bearings to accurate and high tolerances if the cylindrical rollers were perfectly cylindrical and they could be driven while maintaining this desired separating gap. However, it is substantially impossible to make a perfectly cylindrical roll and, accordingly, while the variances may not be noticeable to the eye, when sorting bearings to high tolerances such as 0.000010 of an inch, any variance in the roundness of the cylinder causes changes in the width of the sorting gap.
Examples of sorting devices utilizing rotating cylindrical rolls are disclosed in U.S. Pat. Nos. 1,980,517, 2,314,593, and 1,623,275. Each of these devices are utilized for sorting seeds according to predetermined tolerances and none of these devices would be suitable for sorting bearings to high tolerances such as 0.000010 of an inch.